2. Introduction

Welcome to the CentOS 5.1 release. CentOS is an Enterprise-class Linux Distribution derived from sources freely provided to the public by our Upstream OS Provider (UOP)1.

CentOS conforms fully with the upstream vendors redistribution policy and aims to be 100% binary compatible. (CentOS mainly changes packages to remove upstream vendor branding and artwork.) CentOS is a Free Operating System. The CentOS Project is now accepting donations using PayPal, please see our website at http://www.centos.org for more details. All donations to this project are used to cover bandwidth and development costs.

CentOS 5.1 is the first update to the CentOS 5 distribution series. It contains a lot of bugfixes, updates and new functionality. Before reading any further we advise you to read the UOP release notes at http://www.centos.org/docs/5/. The rest of this document is an addendum, and primarily covers CentOS-specific issues.

3. Known Issues

One of the features added to 5.1 is a new kernel option that allows you to adjust the system clock rate. With this option you can reduce the clock rate from the default of 1000HZ to 100HZ which is desirable in a virtual machine. The official upstream Release Notes states that this option is given as "tick_divider=<value>". However, this is a typo. The correct option is "divider=<value>". Note: the typo has been corrected (Jan 2008).

The CD iso images for the x86_64 architecture released initially were incorrect. CD images 1, 3, 4 ,5 and 6 contained an incorrect timestamp. The master images on central mirror server have been updated with the correct versions. To check that you have the correct version of the images, check the file .discinfo inside each image. The first line should be 1195929648.203590.

The graphical installer is for systems with over 512MB of memory. Using the graphical installer on systems with less than 512MB may cause problems.

The anaconda installer needs at least 128MB of memory to work, and will only use text mode if the system has less than 256MB of RAM.

When you select a lot of packages during a install the amount of memory required and the time to process the dependencies increases. So it is advised that on slower systems or systems with limited memory you do a minimal installation and use yum afterwards to install any missing packages.

Selecting the Extras repository during installation requires that you have a working internet connection. If not Anaconda may hang trying to reach the internet. If you are not performing a network install and have selected the Extras repository then Anaconda will ask you to configure a network interface so that it can reach the internet.

Kickstart scripts that worked for 5.0 may have issues on CentOS 5.1 installation trees. So first test your kickstart scripts with CentOS 5.1 before using them in production.

The CentOS 5.1 kernel has known issues regarding autofs and nfs. These will most likely be fixed in in a future update to CentOS 5.1. More information and a patch can be found in bug report #2448. Note: This issue is fixed by the 2.6.18-53.1.4.el5 kernel update now available in the updates repository.

nautilus-sendto has a require for libgaim.so.0. This file no longer exists in the CentOS-5 tree, as gaim was replaced by pidgin. This is an upstream bug, please see bug report 2483.

During the boot process you may see the message "Memory for crash kernel (0x0 to 0x0) notwithin permissible range" appear. This message comes from the new kdump infrastructure. It is a harmless message and can be safely ignored.

If you use the Virtualization suite (Xen etc.) then the package libvirt will get installed. Since CentOS 5.1 this package has a dependency for dnsmasq, which is a lightweight DNS and DHCP server. If you have any other DNS or DHCP daemons running on the same system you should check that dnsmasq does not interfere with those.

There is a typo in /etc/X11/xinit/Xsession which causes errors to appear in .xsession-errors. This is a known bug (#2258) and will probably be fixed in CentOS 5.2.

The Dovecot package on x86_64 kernels requires the parameter "login_process_size = 64" to be added to /etc/dovecot.conf after an upgrade to CentOS 5.1.

The system-config-httpd webserver configuration program still writes configuration files for httpd-2.0 and not for the included httpd-2.2 webserver (bug #2078). There is no known date or release for a fixed version.

The yum-security plugin allows the user to download specific patches based on bugzilla ID and security fixes for specific CVE and upstream releases. This plugin is not yet working in CentOS 5.1 however we hope to have that fixed in the near future. An independent announcement will be made once its working.

The yum-utils package has been moved from extras to Base by the UOP. In addition, the allowdowngrade, fastestmirror, kernel-module, merge-conf, priorities, refresh-updatesd, repolist, and tsflags yum plugins are also provided in CentOS 5.1.

4. Resolved Issues

The Conga cluster configuration tool (a.k.a. the luci and ricci packages) will now work without the need to make changes to /etc/redhat-release. (Issues #1931 and #2112)

Yum priorities now correctly protects against packages from lower-priority repositories with a different architecture. For instance, against replacement of i386 by noarch packages from a repository with a lower priority.

The yum-cron package has been updated to fix a security issue and clean up the code.

CentOS 5.1 includes a 32 bit version of the perl package for 64 bit installations. The 32 bit package of perl was removed by the UOP in 64 bit installations.

dist.sh now reports correct distro and version on CentOS. dist.sh is a script that identifies and reports the distro release version,. (#2064)

The yum-metadata-parser package contains a metadata parser for yum written in C. It speeds up the metadata parsing phase considerably. It does not change yum behavior in any other way. This package is now installed by default on all CentOS-5 installs as a dependency for yum.

Note: Details of changes can be found in the package changelog. Its also important to keep in mind that most of these packages are only changed to remove upstream branding, as required by their terms of use.

5.4. Packages removed from CentOS that are included upstream

redhat-release-5Client

redhat-release-5Server

redhat-release-notes-5Client

redhat-release-notes-5Server

rhel-instnum

rhn-check

rhn-client-tools

rhnlib

rhnsd

rhn-setup

rhn-setup-gnome

5.5. Packages added by CentOS that are not included upstream

centos-release

centos-release-notes

perl.i386 (on x86_64)

yum-cron

yum-repolist (plugin)

6. Community Involvement

As a CentOS user there are various ways you can help out with the CentOS community.

6.1. Special Interest Groups

CentOS consists of different Special Interest Groups (SIGs) that bring together people with similar interests. The following SIGs already exist:

And we encourage people to join any of these SIGs or start up a new SIG, eg.

Alpha, S390, Sparc port - help with porting CentOS to other architectures

Hardware compatibility - provide feedback about specific hardware

QA - help out with fixing bugs and testing new releases

RPM Packaging - contribute new useful RPM packages

Translation - help translating the documentation, website and wiki content

6.2. Mailinglists and Forums

Another way you can help out others in the community is by joining one of the mailinglists or forums and actively resolve user problems and discuss solutions with others.

6.3. Wiki and website

Even as an inexperienced CentOS user we can use your help. Because we like to know what problems you encountered, if you had problems finding specific information, how you would improve documentation so it becomes more accessible. This kind of feedback is as valuable to others as it would have been to you so your involvement is required to make CentOS better.

So if you want to help out and improve our documentation and wiki, register on the wiki or subscribe to the centos-docs mailinglist.

7. Further Reading

The following websites contain large amounts of information to help people with their CentOS systems :